Acetabular reamers are surgical tools which are used to cut hemispherical cavities in pelvis bones for the insertion of artificial hip joints. The reamer comprises a hemispherical reamer cup, made from surgical stainless steel, having a complex arrangement of cutting surfaces extending outwardly from the hemispherical cup. The reamer cup is attachable to a drive shaft or handle, which in turn can be attached to a drill or the like to provide rotational force.
Acetabular reamers must be capable of producing cavities of very precise dimensions and consequently, the cutting surfaces are generally drilled, worked and sharpened by hand in order to give the required precision. Therefore the manufacturing process for conventional acetabular reamer cups is very skilled, labour-intensive and hence so expensive that it is not economical for the reamer to be disposable. This means that the reamer cup must be intensively cleaned after each use. The cutting surfaces may periodically require re-sharpening as a result of wear in use and/or during cleaning, the re-sharpening being a labour-intensive and skilled task in itself. An example of such a conventional reamer is described in U.S. Pat. No. 4,811,632.
Not only must the reamer cup be cleaned after each use, but also the reusable handle or drive shaft. The junction between the reamer cup and the drive shaft or handle is particularly difficult to clean as it may trap bone particles, dried blood and/or other debris. The interior of the reamer cup described in U.S. Pat. No. 4,811,632 has a cylindrical surface which engages coaxially with the drive shaft, the two being removably secured together by means of a pair of pins extending through holes therein. Alternatively, the reamer cup could be mounted to the drive shaft by engaging threads or discrete fasteners or other equivalent means. All of these moving parts and components provide locations where debris could become trapped, presenting contamination risk and/or problems in fitting the parts together. Undesirable free play between the cup and drive shaft increases wear and decreases the precision of the reamer.
Therefore, it is desirable to provide a simplified and preferably disposable reamer such as that described in U.S. Pat. No. 5,100,267. In U.S. Pat. No. 5,100,267, a disposable reamer cup is provided for use with a reusable drive shaft or handle, wherein the reamer cup is provided with a polymeric plug into which the drive shaft is fitted. The polymeric plug is joined to the reamer cup by detents and intrusions thereon. The drive shaft is attached to the polymeric plug in the same manner as described in U.S. Pat. No. 4,811,632 and, although containing less metal because of the use of the polymeric plug, the reamer cup is manufactured in the same way as described in U.S. Pat. No. 4,811,632.
Consequently, the metal reamer cup is still made using a labour-intensive method, necessary in order to provide the accurately placed cutting surfaces. Furthermore, the number of moving parts and components in the junction between the reamer cup and the drive shaft is not addressed.
It is therefore desirable to provide an improved disposable acetabular reamer or other surgical instrument which seeks to alleviate the disadvantages of the above-described prior art.